DE102008005931A1 - Apparatus for weight-constant portioning of molten glass - Google Patents

Abstract

The invention relates to a device for weight-constant portioning of molten glass, which has a drop reservoir in whose bowl neck a vertically and / or rotationally driven Gewindesegmentplunger is provided and the axial extent of the decisive flow for the part of the Gewindesegmentplungers is smaller than the radius of the bowl neck ,

Description

The The invention relates to a device for weight-constant portioning of molten glass with one over one essentially horizontal gutter from a reservoir with molten glass fed dropper, in its trained as a vertical bore bowl neck and in front of the outlet nozzle in a vertical direction and / or Rotary driven plunger for influencing the through the Gap between bowl neck and plunger flowing Glass is arranged, wherein the plunger in the flow direction of the Glass has a conically widening inflow region, a central region and a diameter-reducing Has outflow area.

A device of this kind is from the DE 198 09 878 A1 known.

such Devices, also referred to as droppers and with smooth Plungers as single or multiple feeders for many decades were used in practice, were in terms of their design and control to achieve higher and higher power further developed, with throughputs of over 200 t / day can be achieved.

The have used in the known devices Schraubenplunger a relative to their diameter relatively large axial Extension and are preferred on its outer surface provided with multi-threaded thread approaches. The such plunger receiving key necks must be there even longer than the plungers, to be flawless Operation of plungers operating in uphill and can move downwards, to ensure. To prevent that from happening thereby resulting, long flow path of the glass itself in the bowl neck unwanted temperature reductions In the glass, usually must in such devices a heating of the often made of platinum bowl neck carried out, which by passing high electrical currents, indirect heating by externally mounted resistance heating elements, can be done by induction heating or the like.

By Although these measures can be the desired Function, but there are also serious ones Increases in equipment costs and also a complication of operation.

Next the desire to increase the performance of standard drop feeders with smooth plungers are also developments towards smaller working speeds which was attempted by reducing the flow cross-section between plunger and bowl neck and a raise the glass viscosity by reducing the glass transition temperature the outflow velocity of the glass from the outlet nozzle with the help of an outside smooth plunger to influence. The problem is that due to the adjusting Cooling of glass often increases the glass melt becomes tough, so that usually the glass portions in no longer work well with the successor machines and frequently Quality losses must be accepted.

task The invention is one, especially for smaller working speeds to provide suitable device of the type specified, which can be realized particularly cost-effective and the delivery of glass portions of optimum temperature and viscosity ensures.

Solved This object is achieved according to the invention essentially by a special design and adaptation of the plunger to the associated bowl neck hole, wherein the axial extent of the flow gap determining cylindrical center region of the plunger is smaller than the radius the bowl neck hole.

By the known up and down movement plunger, in particular in connection with a forward or reverse rotation of the plunger, the glass flow can varies over time as well as within a drop cycle be, wherein the embodiment of the invention the plunger ensures that even at low glass throughputs no disturbing temperature reductions in the molten glass occur and the subsequent processing of the glass problem-free is possible.

Prefers are on the peripheral surface of the cylindrical center region the plunger to create a Gewindegegplungers evenly over the circumference distributed several thread segments provided, each Thread segment of one at the transition from Anströmbereich and mid-range beginning and at the transition from the middle area to the discharge area ending, curved running Web portion is formed. Preferably, the constant Web level possessing web sections in their beginning and end End be slightly beveled formed.

In contrast to multi-turn thread pliers as are conventional in the art, the thread segments formed by land portions are preferably designed in accordance with the invention such that each land portion extends over a circumferential angular range from about 60 to 120 °, preferably 80 to 100 ° of the cylinder outer surface of the central region extends.

The Bridge height is preferably greater than half Width of the gap between middle area and bowl neck selected. Preferably, it is 60 to 90% of Gap width.

in the Traps of extremely slow operation are preferably heated Spout nozzles used to cool the glass Prevent in this area and make sure the glass transition temperature remains largely constant within the glass drop.

to Improve the life of the parts used and improve the glass quality become ceramic thread plunger and bowl neck made of ceramic expediently with a platinum coating which also affects the constancy of the setting values for already optimizes already optimized productions.

The Insert a socket made of platinum or a platinum alloy in the bowl neck or the platinum coating of the bowl neck further prevents wear-related enlargement of the Inside diameter of this bowl neck and thus also an increase in the glass throughput with otherwise the same Parameters.

Further advantageous features of the invention will become apparent from the dependent claims and the following description of an embodiment based on the drawing.

The sole figure of the drawing shows schematically a drop feeder 1 with one below a rotary tube 5 located bowl neck 2 in which there is a Gewindesegmentplunger 4 located.

This thread segment plunger 4 can be moved up and down and is also drivable in both directions.

Of particular importance for the operation with low glass throughputs is the shape of the Gewindegegplungplungers 4 and its dimensioning relative to the bowl neck 2 ,

In comparison to conventional screw pliers and their associated bowl necks, the thread segment plunger used in accordance with the invention has a relatively low overall height, ie the axial extent of the flow gap 8th determining cylindrical central area 9 of the thread segment plunger is smaller than the radius of the bowl neck hole 2 ,

The cylindrically shaped middle area 9 of the thread segmentation plunger 4 is between a substantially conically widening in the flow direction of the glass Anströmbereich 10 and a discharge area 11 located, whose diameter decreases conically towards the free end.

On the peripheral surface of the cylindrical central region 9 of the thread plunger are evenly distributed over the circumference several thread segments 6 provided, each thread segment 6 from one at the transition from upstream area 10 and mid-range 9 beginning and at the transition from middle area 9 to the approach area 11 ending, curved in the manner of a screw section of high pitch extending web portion is formed.

in the illustrated embodiment are four such thread segments shown, but this is not a limiting design represents.

The bridge sections 6 do not run the full size of the mid-range 9 but they expediently extend over a limited circumferential angular range, which may for example be between 60 to 120 ° and in particular between 80 ° and 100 °.

At least over the greater part of its length, the web sections have their maximum height, wherein this maximum web height is greater than half the width of the gap between Gewindesegmentplunger 9 and bowl neck 2 is. Preferably, the web portions extend to close to the wall of the bowl neck 2 ,

During operation of the drop feeder according to the invention 1 are when briefly closing the outlet nozzle 3 with a so-called glass retaining device and a separation of the inevitably somewhat cooled glass, which was in direct contact with the closure plate, with a corresponding drop weight, cycle times of more than a minute reachable. A heating of the outlet nozzle prevents annoying cooling of the glass in this area, even in extremely slow operation, so that the glass transition temperature remains largely constant even within the glass drop.

The thread segment plunger 4 may be made of ceramic material, fused quartz and / or molybdenum and preferably have a coating of platinum or a platinum alloy, in which case in the bowl neck 2 a sleeve of platinum or a platinum alloy forming the surface thereof is used to prevent wear and to keep the life of the parts used and, above all, the quality of the glass high. Instead of using a socket, the Surface of the bowl neck 2 also be provided with a coating of platinum or a platinum alloy.

In order to keep constant the weight constancy of the drops to be formed even at low glass throughputs, the width of the gap 8th between bowl neck 2 and mid-range 9 of the thread segmentation plunger 4 dimensioned such that when stationary Gewindesegmentplunger 4 the average desired flow rate of molten glass adjusts to that of the bowl neck 2 from the essentially horizontal channel 7 is supplied.

That this glass throughput by forward rotation or reverse rotation of the Gewindegegplungplungers 4 has been mentioned above, but in the present case it is important that the desired objectives can be ensured, especially with long cycle times or with a low-throughput glass dropper.

1

Gob feeder

2

bowl neck

3

slice

4

Gewindesegmentplunger

5

rotary tube

6

thread segment (Web portion)

7

gutter

8th

gap

9

the central region

10

inflow

11

outflow region

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 19809878 A1 [0002]

Claims (8)

Apparatus for weight-constant portioning of molten glass with a substantially horizontal channel ( 7 ) fed from a reservoir with molten glass dropper ( 1 ), in which formed as a vertical bore bowl neck ( 2 ) and in front of its outlet nozzle ( 3 ) a vertically and / or rotationally driven plunger ( 4 ) for influencing the through the gap ( 8th ) between bowl neck ( 2 ) and plungers ( 4 ) flowing glass, wherein the plunger ( 4 ) in the flow direction of the glass has a conically widening inflow region ( 10 ), a middle area ( 9 ) and a decreasing in the flow area ( 11 ), characterized in that the axial extent of the flow gap ( 8th ) determining the central cylindrical region ( 9 ) of the plunger ( 4 ) is smaller than the radius of the bowl neck bore ( 2 ). Apparatus according to claim 1, characterized in that on the peripheral surface of the cylindrical central region ( 9 ) of the plunger ( 4 ) evenly distributed over the circumference several thread segments ( 6 ) are provided. Device according to claim 2, characterized in that each thread segment ( 6 ) is formed by a web portion and each web portion over a circumferential angular range of about 60 ° to 120 °, preferably 80 ° to 100 ° of the cylinder outer surface of the central region ( 9 ). Device according to one of the preceding claims, characterized in that each web section over its Height has substantially the same thickness. Device according to one of the preceding claims, characterized in that the maximum web height greater than half the width of the gap ( 8th ) between middle range ( 9 ) and bowl neck ( 2 ) and is preferably about 60% to 90% of the nip width. Device according to one or more of the preceding claims, characterized in that the width of the gap ( 8th ) between bowl neck ( 2 ) and middle area ( 9 ) of the thread segmentation plunger ( 4 ) is dimensioned such that when stationary Gewindesegmentplunger ( 4 ) sets the average desired glass throughput. Device according to one of the preceding claims, characterized in that the existing of ceramic material or fused silica Gewindesegmentplunger ( 4 ) has a coating of platinum or a platinum alloy and in the bowl neck ( 2 ) is used a platinum or platinum alloy socket forming the surface thereof or the surface of the bowl neck is provided with a coating of platinum or a platinum alloy. Device according to one of claims 1 to 6, characterized in that the Gewindesegmentplunger ( 4 ) consists of molybdenum.